FIG. 1 is a block diagram of a conventional Local Area Network (LAN) 10 of a type proliferating in the computing market. These LANs permit a Data Terminal Equipment (DTE) 12, a computer or business machine, which provides data in a digital form, to transfer data and control information with other DTEs 12: Communication from a first DTE 12 to a second DTE 12 is implemented by use of Data Communications Equipment (DCE) 14 which provide functions required to establish, maintain and terminate a connection. DCE 14 provides whatever signal conversion or processing that is necessary or desirable.
There are two interfaces which are important to understand. These include a DTE/DCE interface 16 and a DCE/DCE interface 18, commonly referred to a transmission channel, or medium. For proper and reliable communication, a set of rules for communication between like processes, which provide a means of controlling information transfer between stations (DTEs) on a datalink, known as a protocol are implemented.
A popular protocol referred to as Carrier Sensing, Multiple Access, Collision Detection (CSMA/CD) has been commercially successful. This protocol permits multiple stations to access a LAN system. Each station, before transmitting, will sense a carrier signal indicating that the network presently is being used to transmit a message. If it senses the carrier signal, transmission will not be initiated.
It is possible, due to time delays in propagating a signal from a DTE 12 that two transmissions will overlap. This overlap is referred to as a collision, which will be detected by DCEs 14 on the network. Upon detecting a collision, all transmissions will be terminated and DTEs 12 desiring to transmit will wait a random period of time before attempting to transmit again. This protocol is further defined in IEEE Standard 802.3, hereby expressly incorporated by reference for all purposes, which sets forth requirements for the DTE/DCE interface 16, referenced as an Attachment Unit Interface (AUI). The IEEE Standard 802.3 defines a system which is similar to Ethernet, a registered trademark of Xerox Corporation.
Repeaters are utilized in a LAN network to amplify or regenerate signals passed in the network to compensate for losses. Repeaters will also re-synchronize signals as necessary. Integrated Multiport Repeaters (IMR's) have multiple ports therewithin to receive and transmit multiple data signals.
The IMR includes a carrier sense (CRS) pin which outputs the carrier status of each port. In a preferred embodiment, there are nine (9) ports on the IMR. Typically, the output sequence is the 10 bit serial data stream: LA 01234567, where L=low, A=attachment unit interface (AUI), 0-7=twisted pair port (TP) 0-7.
In normal mode of operation, the serial output pin (SO), serial input pin (SI) and serial clock pin (SCLK) provide management functions for the repeater.
The management function consists of status and controls that are important in complex, high end repeater applications utilized within a LAN network. However, in low end applications, not all the management functionality is necessary. It is important to be able to use an IMR in applications where the complex logic circuitry for providing repeater management status is not needed and still allow the IMR to operate within the IEEE standard set forth for LAN network. It is also important that the IMR be compatible with these standards and still operate efficiently within the context of the particular application. Finally it is important that the IMR be capable of providing support for twisted pair link loopback status, port partitioning status and polarity status signal quality error (SQE). The present invention provides a system that addresses the above-mentioned need.